1. Field of the Invention
This invention relates to a two-way CATV system where a lot of terminal units are connected to what is called a center via cables and the center transmits image signals to the terminal units. It also relates to a remote control system.
2. Description of the Related Art
Recently, the environment of television broadcasting has been encountering a great turning point, especially in the United States. As examples, TV signals for nearly 150 channels in satellite broadcasting and a two-way interactive television signals using cellular phones are now being supplied. Another example is that telephone companies are now making a lot of proposals for and experiments with video service using telephone lines.
In this situation, the CATV systems, which have been a major role in transmitting television broadcast in the U.S., have also been undergoing a revolution. The revolution includes 150-channel near-video on-demand service provided in part of the New York district and the TCI's design for 500-channel transmission. The CATV system, which originally has a very inexpensive transmission system as compared with other media, has the potential of easily implementing the services that are now being realized by other media.
Furthermore, the CATV system itself is rapidly changing its structure and nature. We can point out technical factors for the changes are hybrid transmission as a result of introduction of optical fiber, image compression and transmission techniques. The introduction of optical fiber has not only replaced coaxial cables with optical fibers, but also changed the architecture of the CATV system itself. This is the hybrid structure using optical fibers/coaxial cables obtained in the course of expanding the using frequency band has become comparable in cost with the structure using coaxial cables only. In addition, it should be noted that the hybrid structure explained later is easier to maintain.
A conventional CATV system using coaxial cables has a distribution structure known as a tree and branch, whereas in the hybrid structure using optical fiber/coaxial cables, the portion using optical fibers has a full star structure, and the path from a photoelectric conversion point to a subscriber has a conventional tree and branch structure. Because the number of subscribers supported by the coaxial cables is limited and the optical fiber system has a star structure, the information supplied from the center may differ from node to node. This makes it possible to provide very different service from that in the prior art or to offer the currently available service in a different way.
With the recent advance in image compression technology, an image signal can be compressed to the volume as small as 1/10 to 1/30 that in the prior art. By combining this technology with transmission technology, three to six channels can be transmitted in a 6-MHz band, which was necessary for each channel in the analog system when this transmission line is used as a data channel, it is possible to offer as enormous as several Mbps of separate data channels to each subscriber by linking these techniques with the above-mentioned structures.
Although the subscriber terminals acting as a mere decoder for pay broadcasts should have undergone a revolution, any revolutionized terminal unit has not been proposed yet up to now. In addition, any satisfactory service or service form making use of such an infrastructure has not been proposed either.
Furthermore, concerning the terminal units, a solution to the problem with the conventional equipment, that is, a solution to unfriendly use due to poor connection with other units, has not been given yet. The unfriendly use stems chiefly from the terminal units themselves. For example, to be concrete, some of the causes are a physical wiring problem with TVs and VCRs, the relationship between the remote control unit for one terminal unit and that for another unit, and an interface with multiple TVs.
In the CATV system, in general, TV signal data and data transmitting and receiving facilities known as a center or a head end is connected to subscribers' houses by means of two-way or one-way transmission lines. In each subscriber house, a subscriber terminal unit for pay broadcasts called a converter, a decoder, or a home terminal is installed. With such a system, to provide a subscriber terminal unit with an additional function, the operating company must modify the unit installed in the subscriber's house, which limits its popularization and the cost-effectiveness.
As described above, the system configurations proposed until now are insufficient to meet the diversifying needs of each subscriber arising from the expansion of the contents of CATV service expected in the future. From the viewpoint of the CATV operating company, the maintainability and the expandability are insufficient, either.
On the other hand, household appliances in an ordinary house, especially, a group of video and audio appliances, or what is called audio-visual (AV) equipment, is provided with a remote control function using infrared rays. The group of AV appliances include television sets (TVs), video tape recorders (VTRs), video movies (VMs), optical video disc players (LDs), broadcast satellite (BS) tuners, teletext decoders, compact disc players (CD), and other stereo playback equipment.
Under such circumstances, to select and execute the desired function of each apparatus, it is necessary to operate the remote control unit corresponding to each apparatus. For example, in the case of a single function of viewing a TV program, a single corresponding remote control unit has only to be operated. To achieve a function covering more than one apparatus, e.g., to see and listen to the VTR-reproduced images and sound on a TV, more than one remote control unit must be operated. That is, the operator has to learn the operating procedure for each remote control unit with different specification made by a different manufacturer. He also takes time to find the desired remote control unit. Furthermore, more homes have more than one apparatus of each type, e.g., multiple TVs and VTRs, with the result that the complexity increases as the number of apparatuses increases.
To alleviate the complexity, to operate more than one apparatus with a single remote control unit, there have been provided what is called a learning remote control unit which memorizes the remote control code for each maker's apparatus, and a preset remote control unit for which the remote control codes for more than one maker are set previously.
However, with the learning remote control units, it is necessary to set the codes for the functions of the on-hand apparatus one by one for the learning remote control unit. Thus, as the number of functions increases, the setting procedures tend to increase. That is, the learning remote control unit has the disadvantage that the initial setting is complex. In addition, when a new apparatus is installed, it is necessary to add an operation function in the initial setting.
With the preset remote control units, the complexity of the initial setting found in the learning remote control unit is alleviated remarkably, no product memorizes the codes for all of the apparatuses. Only the major functions are stored in the remote control unit. To operate all functions for all apparatuses, it is necessary to operate together with a dedicated remote control unit provided for each apparatus. Thus, the dedicated remote control unit must be placed at hand, although not frequently.
Setting the learning remote control units etc. in more than one room in a house raises installation costs, because those remote control units have to be paid for, not expensive though, whereas the dedicated remote control units coming with the apparatuses are free of charge. In the case of the learning remote control units, the trouble of the initial setting becomes more serious.
Now, it is assumed that a person having a lot of apparatuses as mentioned above is a subscriber to a CATV system. In a subscriber unit in the CATV system, a converter (a form of terminal) installed in the subscriber's house receives the TV program signal transmitted from the head end (HE), descrambles the program to produce the original image if it is scrambled, converts the image into a predetermined specific channel, and then sends the converted signal to the TV at the subscriber, which displays it. In general, the converter is also provided with a remote control unit, which is basically designed for the converter only and consequently cannot control such peripherals as a TV, a VTR, or an LD satisfactorily. Although having a learning and a preset function, the remote control unit for the converter has the disadvantages of giving us the trouble of initial setting and being unable to control the function of each apparatus sufficiently.
Trouble in connecting the converter with its peripherals will be considered from a different point of view. As a significant example, when telerecording is reserved with a VTR being connected to the converter output, although the VTR starts recording at the reserved time, nothing may be recorded on the VTR in spite of telerecording reservation because neither the power supply for the converter nor its channel is operated. This problem arises from interface mismatching between apparatuses. To overcome this problem, an improvement has been disclosed in U.S. Pat. No. 5,151,789. Specifically, the VTR is provided with means for emulating the converter control code. This means sends the modulated infrared rays to the converter in accordance with VTR operation as if to allow the remote control unit to control not only the VTR but also the converter. Such a series of operations can be performed without giving the user any trouble, making the apparatus more user-friendly. With this method, however, the VTR must be provided with means for emulating the converter remote control code. To implement the function, it is necessary to purchase a new VTR provided with at least an emulation function. This makes the existing apparatus useless, which is uneconomical. In addition, the method has disadvantages in that the initial settings for the aforesaid learning function etc. are necessary and all functions cannot be executed satisfactorily.
As described above, when there are a plurality of AV apparatuses in the house, a conventional remote control system has disadvantages in that the operator must operate more than one remote control unit and learn the operation procedures for each maker's remote control unit, and that he takes the trouble of finding the desired remote control unit, which makes the operation more complex.
To alleviate this complexity, there are provided a learning remote control and a preset remote control, which allows a single remote control to operate more than one apparatus. However, they have disadvantages in that the initial setting is complicated and all of the functions of each apparatus cannot be operated.